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Date: Fri, 22 May 2026 19:54:26 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Dmitry Ilvokhin <d@ilvokhin.com>
Cc: Vlastimil Babka <vbabka@kernel.org>, Suren Baghdasaryan
 <surenb@google.com>, Michal Hocko <mhocko@suse.com>, Brendan Jackman
 <jackmanb@google.com>, Johannes Weiner <hannes@cmpxchg.org>, Zi Yan
 <ziy@nvidia.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 kernel-team@meta.com
Subject: Re: [PATCH v2] mm/page_alloc: fix defrag_mode for non-reclaimable
 allocations
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References: <20260520122228.201550-1-d@ilvokhin.com>
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On Fri, 22 May 2026 13:05:36 +0000 Dmitry Ilvokhin <d@ilvokhin.com> wrote:

> > How serious is this to our users when running real-world workloads?
> 
> We observed it on a few of the Meta workloads that adopted
> defrag_mode=1.
> 
> For the service under load there were 85509 SLUB allocation failures
> messages in dmesg within 2 hours. All of them are GFP_ATOMIC allocations
> for skbuff_head_cache, despite free pages being available in other
> migratetype freelists (~13 GB free).

For a single machine, I assume.

> Since it is networking path from the practical point of view, this means
> dropped packets, failed RPC requests, tail latency spikes and overall
> service degradation.

OK, thanks.   I assume 12 failures per second isn't a disaster, and that
there's no need to fast-track this into 7.1?